Door operator



Oct. 27, 1959 1.. B. M. BUCHANAN DOOR 1 OPERATOR 4 Sheets-Sheet; 1

Filed Jan. 3, 1957 Oct. 27, 1959 L. B. M. BUCHANAN 2,910,290

DOOR OPERATOR Filed Jan. 5, 1957' 4 Sheets-Sheet 2 DOOR OPERATOR 4 Sheet s-Sheet 5 Filed Jan. 3, 1957 L. B. M. BUCHANAN 2,910,290

Oct. 27, 1959 DOOR OPERATOR 4 Sheets-Sheet 4 Filed Jan. 3, 1957 United States Patent DOOR OPERATOR Application January 3, 1957, Serial No. 632,340

8 Claims. (Cl. 268-65) This invention relates to apparatus for automatically opening and closing doors and in particular to a device which will open, hold open and close the door and which requires a minimum amount of efiort by the operator.

It is an object of the present invention to provide an automatic device to open a door, hold the door open for a predetermined period of time, and to automatically close the door.

It is a further object of the invention to provide an automatic door opening and closing mechanism which maybe easily actuated by the operator.

In many instances where an automatic door opening and closing mechanism is used it may be desirable to in tenmpt the normal cycle or to prolong or curtail the open, period. Therefore, it is a further object of this in vention to provide an automatic door operating device, the normal opening and closing cycle of which may be interrupted by the operator without damage to the operating mechanism.

Another object is to provide an automatic door opening and closing mechanism Which, after the normal operating cycle has been interrupted, may be easily restored to the initial position for automatic operation.

In the automatic door opening and closing mechanism of this invention, a pair of springs are employed to store energy and impart opening and closing movement to the door. A first or opening spring is adapted to be maintained. in stressed condition while the door is closed, and upon the door becoming unlatched, the energy stored in this; opening spring is transmitted through a linkage mechanism to the door, moving the door to its open position. The second or closing spring is arranged in such a mannor as to bias the door toward its closed position and is partially stressed as the door is moved to its open position under the action of the opening spring.

This invention also contemplates the use of a source of motive power, such as an electric motor, which is adapted tobe energized when the door is in its open position to act on the linkage mechanism to stress both the opening and closing springs; in other words, the electric motor provides energy which is stored in the closing spring and subsequently dissipated when the door is permitted to close, and also provides energy which is stored in the opening spring for subsequent use in the next door opening operation. Suitable control circuits are provided for energizing and deenergizing the electric motor to store energy in the springs during periods when the door is open.

A further feature of the invention is the employment of the electric motor as a timing means to release the door from its open position and permit it to close after the lapse of a predetermined period of time following opening of the door.

The foregoing and other objects are effected by the invention as will be apparent from the following description taken in connection with the accompanying drawings, forminga part of this application, in which:

Fig. 1 is a view, in perspective, of a typical refrigerator s ce cabinet showing schematically a door latch and a door operating mechanism, the latter being constructed in accordance with the present invention;

Fig. 2 is a plan view of the door operating mechanism when the door is in the closed position;

Fig. 3 is a sectional view, taken along the line III-III of Fig. .2, looking in the direction indicated by the arrows;

Fig. 4 is a plan view, similar to Fig. 2 but showing the door operating mechanism when the door is being opened and is intermediate the closed position and the open position;

Fig. 5 is a plan view, similar to Figs. 2 and 4, but showing the door operating mechanism when the door is in the open position;

Fig. 6 is a sectional view taken along line VI-VI of Fig. 5. looking in the direction indicated by the arrows;

Fig. 7 is a fragmentary plan View showing the position and operation of a portion of the mechanism as the door is being closed; and

Fig. 8 is a schematic wiring diagram of the apparatus.

Referring to the drawings and in particular to Fig. i, there is illustrated a domestic refrigerator having a door 12 and a cabinet 14. The door 12 is provided with a suitable latch 16 and a door operating device 18 which are shown only schematically in Fig. 1 and will be described subsequently. Generally, the door operating device 18 serves to open, maintain open and close the door 12 without any manual effort by the operator except to release the latch 16, which may be either of the mechanical or magnetic type, both types being well known in the art and, therefore, not illustrated in detail. An embodiment of the present invention has been constructed to open the door in approximately two seconds, hold the door open for approximately eight to ten seconds, and then close the door in approximately three more seconds. As will become apparent as the detailed description proceeds, these time periods can be varied.

Referring to Figs. 2 and 3, there is shown in detail the door closing mechanism as it appears when the door has been in the closed position for a period of time. The mechanism 18 is preferably mounted within the cabinet 14 and, when applied to a refrigerator, can be located within the unrefrigerated machinery compartment in the lower portion of the cabinet. The door 12 is provided, on the right-hand side as viewed in Fig. 2, with a hinge 19 which is secured to the cabinet 14 for pivoting the door about a vertical axis. The door is connected to the operating mechanism by a suitable link 22, hereinafter referred to as an actuating arm. The actuating arm 22 projects through an opening 15 in the front of the cabinet 14 and transmits to the door 12 the forces required for opening and closing the door. The actuating arm 22 is pivotally connected to a bottom panel 21 of the door 12 by a pin 23.

The forces for opening and closing the door are provided, respectively, by a pair of springs 24 and 26, which, in all positions of the device, are in tension. One end of each spring is connected to a J-shaped link 28, hereinafter referred to as a pivot arm. The pivot arm 28 pivots, about a pin 29 mounted on a stationary supporting plate 25 of the door actuating mechanism. Thesupporting plate 25 is secured to the cabinet by any suitable fastening means (not shown). The opening spring 24 has one end attached to. one end 42 of the pivot arm 28 and. the other end to a portion of the cabinet 14 near the vertical axis of the hinge 19. The closing spring 26 is also attached at one end to the pivot arm 28 adjacent the point of attachment for the opening spring 24. Theother end of the closing spring 26 is attached to a projection 30 extending from the actuating arm 22.

when thedoorlz. is closedthe actuating arm 22 is:

in its innermost position as shown in Fig. 2. The actuating arm 22 is positioned between a plurality of rollers 36 and 38 and has an end portion 27, farthest removed from the pin 23, in contact with a push roller 39 pivotally mounted onthe pivot arm 28. Roller 36 is carried by a fixed pivot pin on the supporting plate and roller 38 is mounted on a plate member 40 pivotally mounted at 41 and biased against the actuating arm 22 by means of a spring 37 for a purpose which will hereinafter be described. The push roller 39 is preferably mounted on the pivot arm 28 in a position midway between pivot pin 29 and the end portion 42 to which the springs 24 and 26 are attached.

The pivot arm 28 is provided with a follower 31 which cooperates as hereinafter described with a cam 32, driven by a motor 33, for the purpose of storing the required energy in the closing and opening springs. In the closed position, (Fig. 2) the follower is displaced from the center of the cam a distance approximately equal to the maximum cam rise. The cam 32 is mounted on the shaft of motor 33 for clockwise rotation therewith as indicated by the arrow in Fig. 5. The cam 32 preferably possesses a single rise, spiral peripheral surface with the high and low portions of the cam surface joined by a radial peripheral portion. In the static door closed position shown in Fig. 2, the cam 32 rests in a position in which the low point of its peripheral surface is opposite the cam follower 31 on the pivot arm 28. The follower 31 is out of contact with the cam 32 by virtue of the door 12 being closed and latched and the pivot arm 28 being held in the position shown by the actuating arm 22.

The cam motor is controlled by a switch 46 of the normally closed type and which is mounted on a plate 52. The plate 52 pivots about a pin 47 secured to the plate 25 and is biased clockwise by a spring 59. In the door closed position, a finger portion 50 of the actuating arm 22 engages a bumper 52a on the support plate 52, holding plate 52 and switch 46 thereon against the bias of spring 59 in the position illustrated in Fig. 2, which is hereinafter identified as position A. In position A, a leaf 49 extending from the switch 46 is biased to the right by a pin 48 provided on the cam 32 in such a manner that the switch is open, and the motor 33 which drives the cam is deenergized.

When the door 12 is in the closed position, the pivot arm 28 occupies the extreme counterclockwise position of its range of movement about pivot pin 29. In this position the opening spring 24 is stretched beyond its normal length, i.e., it is stressed and it applies a bias to pivot arm 28, tending to rotate arm 28 clockwise. Consequently, in the closed position the push roller 39 attached to the pivot arm 28 is in contact with the end portion 27 of the actuating arm 22 and transmits the bias of spring 24 through the actuating arm 22 to the door 12. A counterclockwise moment exists about the vertical axis of the hinge 19, and the door will open when the latch 16 is released.

When it is desired to open the door 12 the operator releases the latch 16. Since the door 12 has been under a force tending to open it, the door immediately starts to pivot about its hinge axis. Fig. 4 illustrates the position of the device when the door is in a position intermediate the fully closed and fully open position and shows the door while it is still being pushed by the action of the push roller 39 hearing against the end portion 27 of the actuating arm 22 and before it reaches its maximum velocity.

Upon release of the latch 16 and the movement outwardly of the actuating arm 22 so that the finger portion 50 thereof no longer contacts the switch support 52,

the latter rotates clockwise under the influence of the biasing spring 59, until the switch support 52 assumes position C, shown in Fig. 4 and indicated 'by dotted lines in Fig. 2. The edge of support plate 25 acts as a stop for the switch support plate 52. Just before the cam follower 31 contacts the cam 32 a roller projection 51 on the actuating arm 28 engages another bumper 52b on support plate 52 and rotates the switch support plate counterclockwise about pin 53 to position B (shown in Fig. 5 and indicated by dotted lines in Fig. 2).

Pressure of the cam pin 48 on the switch leaf 49 is relieved and the switch closes, energizing the cam motor 33-. Thus, the cam 32 starts rotating while the door is moving from approximately its half open position to its fully open position.

When the cam follower 31 comes in contact with a portion of the cam 32 near the minimum diameter of the cam the door has reached a point of maximum velocity. The point of maximum velocity occurs at approximately the midpoint between fully open and fully closed positions and thereafter the door glides or decelerates to the fully open position.

-Movement of the door 12 to the position shown in Fig. 5 (the fully open position) is due to the inertia of the door and results from the energy stored in the door 12 by the opening spring 24. The latter portion of door opening movement is dampened by the closing spring 26 which is stressed or stretched slightly as the actuating arm 22 is pulled out of contact with the pivot arm roller 39. It will be noted that, whereas the pivot arm 28 and the actuating arm 22 moved in the manner of a connected linkage assembly during the initial portion of the door opening movement when the pivot arm 28 was pushing against the actuating arm 22 through the roller 39, during the latter portion of opening movement of the door 12, motion of the actuating arm 22 becomes independent of the pivot arm 28 as movement of the pivot arm 28 is stopped 'by virtue of the pivot arm follower 31 contacting cam 32. There is then, in effect, a lost motion connection between the actuating arm 22 and the pivoted arm 28 which allows the door 12 to swing out to its fully open position, separating the actuating arm 22 from the pivot arm 28 and partially stressing the closing spring 26 connected between the arm 22 and the arm 28. The damping or braking action of the closing spring 26 on the door 12 brings the door 12 to a gentle halt in its fully open position.

Referring to Fig. 5, the door 12 is shown in its fully open position in which the actuating arm has been pulled outwardly by the door 12 until a holding notch 53 near the free end of the actuating arm 22 moves opposite the arm guide roller 38. The roller 38, being biased toward the actuating arm 22 by the spring 37, moves into the holding notch 53 and acts as a detent to releasably lock the actuating arm 22 against further movement. The door 12 is thereby held in its open position.

In accordance with this invention, the motor 33, cam 32, and the pivot arm 28 driven thereby are employed as a'timing mechanism to determine the period of time the door 12 is held in its open position before being automatically closed. As mentioned previously, the motor 33 is energized to impart clockwise rotation to the cam 32 upon the pivot arm 28 reaching its extreme clockwise position. As cam 32 rotates, it drives pivot arm 28 counterclockwise about pivot pin 29, stressing or stretching both the opening spring 24 and the closing spring 26. Stressing of closing spring 26 increasingly biases the actuating arm 22 inwardly of the cabinet. Movement of the actuating arm 22 in the direction to close the door 12 is, however, resisted by engagement of roller 38 in the holding notch 53 until near the end of the counterclockwise rotation of the pivot arm 28, when a stop roller 55, which is carried by the pivot arm 28, comes in contact with a projection 56 on the hold-open plate 40 The hold-open plate 40 is rotated clockwise until the roller 38 moves out of the notch 53 releasing the actuating arm 22. The closing spring 26, which was stretched to more than its normal length by movement of the pivot arm 28, then pulls the actuating arm 22, and, hence, the door 12 toward closed position.

Prior to the door 12 being returned to its fully closed position, the bias applied to pivot arm 28 by the springs 24 and 26 is opposed solely by virtue of follower 31 bearing on the cam '32. It is necessary that the pivot arm 28 be held in its extreme counterclockwise position until such time as the actuating arm 22 is moved inwardly and contacts the pivot arm roller 39 to hold the arm 28 in such position. Means are provided for stopping rotation of the cam 32 just prior to the position at which it would release the follower 31. Stated diiferently, the cam 32 is prevented from continuing its clockwise rotation to the point where the follower 31 would ride off the high point of the cam and allow the pivot arm 23 to slam around clockwise in an unrestrained manner under the action of springs 24 and 26.

This stopping of the rotation of cam 32 with its high point still adjacent the follower 31 is accomplished by means of the switch 46 controlling energization of the motor 33 and illustrated in Fig. 7 of the drawings. The full line showing of the elements of the mechanism depicts the positions of these elements just as the motor driving cam 32 is deenergized and while the door is still open. It will be noted that the pivoted switch support 52 is biased to its extreme clockwise position (position C). This locates the switch blade 49 in a position to be engaged by the cam pin 48 to open the switch 46 when the cam 32 reaches the full line position shown in Fig. 7.

As the door 12 closes, the finger portion 50 of the actuating arm 22 comes in contact with the bumper 52a of the switch support 52 and rotates the switch counterclockwise, to position A. This is shown in dotted lines in Fig. 7. In this manner the leaf 49 is moved away from or out of the way of the pin 48 and the switch is again closed. T hereupon, the cam 32 rotates and the cam follower 31 moves off the high part of the cam and assumes a position opposite the low part of the cam so that it is ready for the next opening. Simultaneously with the switch closing, the door latch 16 secures the door 12 in the closed position. The cam motor 33 is then deenergized, by the cam pin 43 contacting the switch blade 49 (see dotted line positions), after the cam 32 has rotated through the small angle necessary to clear follower 31.

An electrical wiring diagram for the automatic door opener and closer of this invention is shown in Fig. 8 of the drawings. In this figure, portions of the operating mechanism are illustrated in diagrammatic fashion and the reference numerals applied thereto are the same as those previously used in the detailed description of the mechanism. Electrical energy is supplied to the drive motor 33 from a pair of supply lines identified as L1 and L2 by means of one line 61 connected directly to the motor 33 and another line 62 connected to the motor 33 through the switch 46 previously described. Switch 46 is normally closed and is actuated to its open position by switch blade 49 when engaged by cam pin 48. Supply lines L1 and L2 also supply current for the actuation of the latch mechanism 16 which is shown schematically in Fig. 8 as a simple solenoid actuated device. The latch 16 consists of a strike 63 carried by the cabinet 14 in a position to be engaged by a bolt 64 carried by the door 12. The bolt 64 is retracted from the strike 63 to unlatch the door 12 from the cabinet 14 by means of a solenoid 65. Electric current from supply lines L1 and L2 is supplied to the solenoid 65 by means of lines 66 and 67, the line 67 being wired through a normally open switch 68 adapted to be closed by a handle 69 for the latch mechanism.

In operating the latch 16 the operator pulls on the handle 69, closing the switch 68 and energizing the solenoid 65 which retracts the bolt 64. It will be obvious to those skilled in the art that the handle 69 and the switch 68 may be replaced by a push button (not illustrated) located either on the cabniet 14, the door 12 or a remote location. The door 12 is thus released from the cabinet 14 and permits the door to swing open under the bias of the opening spring 24. Thereafter the automatic opening and closing mechanism commences to operate in the manner previously described with energization of the motor 33 being controlled by the switch 46.

The automatic door opening and closing mechanism of this invention is so constructed that either or both the door opening movement and the door closing movement of the door 12 may be manually accelerated by the operator or the door may be closed prior to the end of the automatically timed open period without injury to the drive mechanism. If the operator, upon releasing the latch 16, accelerates the door opening movement by manually pulling on the door 12, the mechanism will function normally with the opening spring 24 causing the pivot arm 28 to follow the actuating arm 22 as it moves out of the cabinet 14. With an extreme manual door opening movement, the door is prevented from opening too far by the arm 22 butting a portion of the cabinet 14 adjacent the opening 15 through which the arm 22 extends. The remainder of the mechanism functions normally to rotate the pivot arm 28 in the direction to stress the opening spring 24 and closing spring 26 for subsequent automatic operation. If, during the course of an automatic closing movement of the door, the door is manually pushed toward its closed position, the actuating arm 22 will merely slide between its guide rollers 36 and 38 until it engages the push roller 39 on the pivot arm 28. The door 12 may also be manually closed prior to the time that it would otherwise automatically close. If the motor driven cam 32 has not returned the pivot arm 28 to its extreme clockwise position, a manual closing force applied to the door 12 is transmitted through the actuating arm 22, causing the pivot arm 28 to override, so to speak, the cam 32, and movement of the pivot arm 28 to its extreme counterclockwise position is accelerated. With the door 12 thus manually closed and latched the cam 32 will continue to be driven without load until it reaches the position shown in Fig. 2, where its drive motor 33 becomes deenergized.

If it is desired to keep the door open for a greater period of time than provided by the revolution of the cam 52, it is only necessary to manually move the door beyond the fully open position shown in Fig. 5 a distance suflicient to cause roller 38 to ride out of holding notch 53 and engage a second notch 54. This additional movement of the actuating arm 22 brings an offset portion 57 of the actuating arm 22 into contact with the guide roller 36, shifting this end of the arm 22 in the direction of roller 38 and causing the spring biased plate assembly 40 to rotate clockwise sufliciently to clear the projection 56 from the path of the release roll 55 on the pivot arm 28. Arm 22 will remain in this position, even though pivot arm 28 is driven to its counterclockwise stopped position (full line position of Fig. 7 until the door 12 is manually nudged toward its closed position to move roller 38 out of notch 54.

It should be apparent that the period of time required for a complete door opening, hold open, and door closing cycle of the mechanism of this invention is determined by a number of factors which, for any given application, may be adjusted to provide a predetermined door open period. These factors are: (a) the period of time required for the opening spring 24 to move the pivot arm 28 to its extreme clockwise position. This time period is determined by the strength of the spring 24 with respect to the inertia mass of the door 12; (b) the time period required for the cam 32 to make substantially a complete revolution to move the pivot arm 28 from its extreme clockwise position to its extreme counterclockwise position to release the roller 38; and (c) the strength of the closing spring 26 with respect to the inertia mass of the door 12, which factor determines the period of time required to actually close the door. By increasing the speed of rotation of motor 33, the time required for the cam 32 to make one revolution can be reduced and the period that the door is automatically held open can be decreased. Conversely, decreasing the speed of the motor 33 increases the period of time required for the cam 32 to make one revolution and the door open period can thus be increased. The mass of the door 12, for most applications, will remain substantially constant and changes in the rate at which the door is opened and closed may be adjusted by varying the strength of the opening and closing springs 24 and 26.

From the foregoing it will be apparent that this invention provides an improved mechanism for opening, holding open and closing entirely automatically, virtually any type door for which automatic actuation is desired.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various other changes and modifications without departing from the spirit thereof.

What is claimed is:

1. In an operating mechanism for a door that is movable between open and closed positions, a spring for opening said door, means restraining one end of said spring, means for connecting the other end of said spring to said door, said last-named means including a member mounted for movement between first and second positions, the other end of said spring being connected to said member whereby said spring is adapted to move said member from its first to its second position, and lost mo tion structure for transmitting movement of said memher to said door to cause said door to move from its closed position to its open position when said member moves from its first position to its second position, said lost motion structure permitting rnvement of said member from its second position to its first position independently of said door, motor means for returning said member from its second position to its first position and for holding said member in its first position, means actuated by said member upon reaching its second position for energizing said motor means to efiect return of said member to its first position, means responsive to closing of said door for rendering said motor means ineffective to hold said member in its first position, whereby said member transmits the force of said spring to said door to bias said door toward its open position, and releasable latch means for holding said door closed against the bias of said spring.

2. in an operating mechanism for a door that is movable between open and closed positions, a releasable latch for holding said door in its closed position, a spring for opening said door, means restraining one end of said spring, means for connecting the other end of said spring to said door, said last-named means including a member mounted for movement between first and second positions, the other end of said spring being connected to said member whereby said spring is adapted to move said member from its first to its second position, and lost motion structure for transmitting movement of said member to said door to cause said door to move from its closed position to its open position when said member moves from its first position to its second position, said lost motion structure permitting movement of said member from its second position to its first position independently of said door, means including a source of motive power for returning said member from its second position to its first position and for holding said member in its first position, means actuated by said member upon reaching its second position for energizing said motive power means to effect return of said member to its first position, and means responsive to closing of: said door for rendering said motive power means ineffective to hold said member in its first position, whereby said member transmits the force of said spring to said door to bias said door toward its open position while said door is held closed by said latch.

3. In an operating mechanism for a door that is movable between open and closed positions, a spring for opening said door, means restraining one end of said spring, means for transmitting the force of said spring to said door and including a member mounted for movement between said first and second positions, said spring having the other end thereof connected to said member whereby said spring biases said member toward its second position, and lost motion structure for transmitting movement of said member to said door to cause said door to move from its closed position to its open position when said member is moved from its first position to its second position under the action of said spring, said lost motion structure permitting movement of said member from its second position to its first position independently of said door, a motor, a cam driven by said motor and engageable with said member for moving said member from its second position to its first position, means actuated by said member upon reaching its second position for energizing said motor, means responsive to return of said member to its first position for deenergizing said motor with said cam in position to hold said member in its first position, and means responsive to closing of said door for energizing said motor to drive said cam out of engagement with said member to release said member and permit said spring to bias said door toward its open position.

4. In an operating mechanism for a door that is movable between open and closed positions, a latch for holding said door in its closed position, a spring for opening said door when said latch is released, means restraining one end of said spring, means for transmitting the force of said spring to said door and including a member mounted for movement between said first and second positions, said spring having the other end thereof connected to said member whereby said spring biases said member toward its second position, and lost motion structure for transmitting movement of said member to said door to cause said door to move from its closed position to its open position when said member is moved from its first position to its second position, said lost motion structure permitting movement of said member from its second position to its first position independently of said door, a motor, a cam driven by said motor and engageable with said member for moving said member from its second position to its first position, means actuated by said member upon reaching its second position for energizing said motor, means responsive to return of said member to its first position for deenergizing said motor with said cam in position to hold said member in its first position, and means responsive to closing of said door for energizing said motor to drive said cam out of engagement with said member to release said member and permit said spring to bias said door toward its open position.

5. In a mechanism for opening and closing a door, the combination of a member mounted for movement between first and second positions, a first spring for moving said member from its first position to its second position, motive means for moving said member from its second position to its first position against the action of said spring, means including lost motion structure for transmitting motion of said member to said door for causing said door to move from its closed position to its open position when said member is moved from its first position to its second position by said spring, said lost motion structure permitting movement of said member from its second position to its first position independently of movement of said door, means actuated by said member upon reaching its second position for initiating operation of said motive means to return said member to its first position, a second spring, and means connecting said second spring to said member and to .said door whereby said second spring is stressed in a manner to bias said door toward its closed position when said member is moved from its second position to its first position.

6. In a mechanism for opening and closing a door for a cabinet, the combination of a member mounted for movement between first and second positions, a first spring for moving said member from its first position to its second position, motive means for moving said member from its second position to its first position against the action of said spring, means including last motion structure for transmitting motion of said member to said door for causing said door to move from its closed position to its open position when said member is moved from its first position to its second position by said spring, said lost motion structure permitting movement of said member from its second position to its first position independently of movement of said door, means actuated by said member upon reaching its second position for initiating operation of said motive means to return said member to its first position, a second spring, means connecting said second spring to said member and to said door whereby said second spring is stressed in a manner to bias said door toward its closed position when said member is moved from its second position to its first position, means for holding said door in its open position against the bias of said second spring, and means for rendering said holding. means ineffective when said member is returned to its first position.

7. In an operating mechanism for a door movable between open and closed positions, an arm connected to said door for moving the door between its open and closed positions, a member mounted for reciprocating movement between first and second positions, said member being engageable with said arm while moving from its first position to its second position to effect movement of said door to its open position, a door opening spring having one end thereof connected to said member, means restraining the other end of said spring whereby said spring biases said member toward its second position for opening said door, a closing spring connected to said member and said arm and adapted to be stressed by movement of said member from its second position to its first position when said door is in its open position, releasable means for holding said door in its open position against the bias of said closing spring, means functioning over a predetermined period of time for returning said member from its second position to its first position, and means for releasing said holding means when said member is returned to its first position.

8. In an operating mechanism for a door movable between open and closed positions, an arm connected to said door for moving the door between its open and closed positions, a member mounted for reciprocating movement between first and second positions, said member being engageable with said arm while moving from its first position to its second position to eifect movement of said door to its open position, a door opening spring having one end thereof connected to said member, means restraining the other end of said spring whereby said spring biases said member toward its second position for opening said door, a closing spring connected to said member and said arm and adapted to be stressed by movement of said member from its second position to its first position when said door is in its open position, releasable means for holding said door in its open position against the bias of said closing spring, motor means for returning said member from its second position to its first position, means for activating said motor means when said member reaches its second position, and means for releasing said holding means when said member is returned to its first position.

References Cited in the file of this patent UNITED STATES PATENTS 1,129,391 Hohne et a1. Feb. 23, 1915 1,538,103 Fanders May 19, 1925 1,628,011 Tompkins May 10, 1927 1,773,243 Stewart Aug. 19, 1930 1,992,198 Dushane Feb. 26, 1935 2,634,970 Rosebrook Apr. 14, 1953 2,710,186 Maurer June 7, 1955 

